I'm going to replace a rear quarther panel,so when i cut and replace the panel do i need to leave metal to make a flange out of?
doitmopar,
I just got done replacing the right 1/4 on my '69 project car. This was the first 1/4 skin I've ever replaced. On the repro 1/4, I cut off the top flange, the rear where it turns back to the tail light panel, & the front where it turns into the door jamb. Basically, I was left with a big "patch panel."
On the car, I left the original metal back at the tail light panel, the rear bumper impression, and the original door jamb opening. I left about 1 inch below the top body line, and about 1-1/2 in from the door jamb & rear area of the 1/4. I then flanged the top and front (door) area. I did not flange the back, as the rear 1/4 came pretty close to the back line & I was able to feather in the filler quite nicely there.
I used 3M's bonding adhesive all around the bottom flanges : trunk floor extension, wheelhouse, & rocker panel. This is super-strong stuff, & I used it for corrosion protection as well as strength in the lower areas. It is designed for this use. I then welded all the outer/upper areas, 1 tack at a time spacing them out about a foot or so. Once 50% welded or so, I started cleaning up my welds with a grinder. I did not completely weld it up & then grind, as I did'nt want to warp the panel from heat from grinding, either.
I ground those down, did some more welding, grinding, welding, etc. Once fully welded & ground, I gave it a skim coat of Evercoat's Duraglas filler & sanded it smooth. I primed it with PPG's DP gray epoxy primer, & now it's ready for final plastic/body filler work. I like to do the plastic work over the DP primer, it feathers real nicely, & sticks better than over bare steel.
For the inside, you have a seam to deal with. Instead of welding the inside, & gave it a coat of the 3M's bonding adhesive again & smoothed it out with a small throwaway brush. So, the 1/4 is welded from the outside, & bonded on the inside. It's not going anywhere! The bonding adhesive flows out real nicely as it dries, so once I give it a thick coat of the sound deadener or undercoating you won't see the seam.
I'll try to post some pics later.
Good Luck!